Animal experts are baffled since 1,000 toads have exploded without warning in the German city of Hamburg.
Eyewitnesses say they've seen the amphibians swell to up to four times their normal size, before bursting.
Some vets think the strange deaths could be linked to a fungus spread from horses at a nearby race course, causing the toads to swell and split.
Officials are worried all the toads in Hamburg may be dying out.
Nature protection worker Werner Smolnik said more than 1,000 toads died after exploding during the last four days.
"You see the toads crawling along, swelling as they go, until they are like little tennis balls and then they suddenly explode," said Mr Smolnik.
The explosions usually happen at night but environmental officials are warning people to watch out for toad blasts in parks.